As of this moment, there are three Cython modules in Numpy, so yes. Releases ship the C generated modules, so it is not a dependency.

./numpy/distutils/tests/pyrex_ext/primes.pyx
./numpy/random/mtrand/mtrand.pyx
./tools/allocation_tracking/alloc_hook.pyx

In any case, we should always include a single threaded version because sometimes the computations are already parallelised at a higher level.

Is there a nice way to ship both versions? After all, most implementations of BLAS and friends do spawn OpenMP threads, so I don't think it would be outrageous to take advantage of it in more places; provided there is a nice way to fallback to a serial version when it is not available.

/David.